The D TECH™ BTEX Immunoassay Test System (Benzene, Toluene, Ethylbenzene, and Xylenes in Water and Soil).

Chapter 412, Section 25200.1.5, Health and Safety Code, enacted by Assembly Bill 2060, Weggeland 1993, authorizes DTSC to certify the performance of hazardous waste environmental technologies. Only technologies that are determined not to pose a significant potential hazard to the public health and safety or to the environment when used under specified operating conditions and which can be operated without specialized training and with minimal maintenance may be certified. Incineration technologies are explicitly excluded from the certification program.

The purpose of the certification program is to provide an in-depth, independent review of technologies at the manufacturer's level to facilitate regulatory and end-user acceptance and to promote and foster growth of California's environmental technology industry.

DTSC makes no express or implied warranties as to the performance of the manufacturer's product or equipment. The end-user is solely responsible for complying with the applicable federal, state, and local regulatory requirements. Certification does not limit DTSC's authority to require additional measures for protection of the public health and the environment.

By accepting certification, the manufacturer assumes, for the duration of certification, responsibility for maintaining the quality of the manufactured equipment and materials at a level equal or better than was provided to obtain certification and agrees to be subject to quality monitoring DTSC as required by the statute under which certification is granted.

DTSC's notice of intent to certify was published on April 14, 1995 in the California Regulatory Notice Register Volume 95, No. 15-Z, p.633-641. Written comments in relation to the proposed certification received during the public review and comment period have been duly considered in the final certification as presented here. DTSC's final certification shall become effective on Monday, July 31, 1995.

Additional information supporting the DTSC's final certification decision is available for review at:

Under the authority of Section 25200.1.5 of the California Health and Safety Code, DTSC hereby certifies the D TECH BTEX Immunoassay Test System (Benzene, Toluene, Ethylbenzene, Xylenes in Water and Soil) distributed by E Science and manufactured by Strategic Diagnostics, Inc., as a Measurement Technology. The assay system uses immunosorbent assay technology. It differs from other systems in that polyclonal antibodies are attached to latex particles and a non-enzyme color development procedure is used. BTEX in water is assayed directly; for soils, the system uses a methanol extract. The minimum detection limit of the D TECH system is defined as four standard deviations above zero concentration. At this reference level, the probability of avoiding false negative results is expected at the 99.9% confidence level. In recent runs of 30 samples each, no false negative results were observed with water and soil samples. Detection ranges are from 0.6 to 10 ppm for water and from 2.5 to 35 ppm for soil. Ranges can be extended upward by dilution of the extracts. The calibration of this product is based on a BTEX standard which consists of a pure mixture of benzene, toluene, ethylbenzene, and xylenes in a ratio of 4:55:8:33 (according to the relative proportion of BTEX compounds in a standard gasoline formulation proposed by U.S. EPA in 1988). The assay responds quite well to benzene with a cross-reactivity of 39% relative to the BTEX standard (100%). There is some cross-reactivity (5 to 11%) with naphthalene and polynucleated aromatics and little or no response to the alkanes tested.

The assay can be recalibrated in terms of other petroleum fuels with the option of developing appropriate conversion factors relative to the original calibration. Quantitation in this assay is by matching the color produced in the latex particles retained on a filter against a color card for a semiquantitative result. Alternatively, a numerical result can be read from the D TECTOR®, a hand-held, battery-operated meter.

Due to high volatility of the constituents of BTEX, recovery and precision of the results from soils can vary significantly. The effect of soil type, moisture content, organic substances and interferences at the site need to be taken into consideration when interpreting the results. Conditions of sample handling are important. For samples that are to be transported to a laboratory, users should follow U.S. EPA guidelines for sample storage and transportation, and a travel blank prepared from reagent water should be carried with all samples to ensure that no volatile organics leak or diffuse into the sample vial during shipment and handling.

Limitations of Certification

DTSC makes no express or implied warranties as to the performance of the manufacturer's product or equipment. DTSC has not conducted any bench or field tests to confirm the manufacturer's performance data. Nor does DTSC warrant that the manufacturer's product or equipment is free from any defects in workmanship or material caused by negligence, misuse, accident, or other causes.

DTSC believes, however, that the manufacturer's product or equipment can achieve performance levels set out in this Certification. Said belief is based on a review of the data submitted by the manufacturer and other information, and is based on the use of the product in accordance with the manufacturer's specifications.

This Certification is issued as part of a pilot project to expedite the California Environmental Technology Certification Program. As a result, this Certification is subject to the conditions set out in the regulations to-be-developed, such as the duration of the Certification, the continued monitoring and oversight requirements, and the procedures for certification amendments, including decertification.

By accepting this Certification, the manufacturer assumes, for the duration of the Certification, responsibility for maintaining the quality of the manufactured materials and equipment at a level equal or better than was provided to obtain this Certification and agrees to be subject to quality monitoring by DTSC as required by the law under which this Certification is granted.

Specific Conditions

Through updates of user guides, manufacturer shall inform the user of interferences and matrix effects which potentially affect the testing results as they become known to the manufacturer.

Basis for Certification

This Certification is based on the evaluation of documents provided by the manufacturer and on independent evaluations which support performance claims consistent with this Certification. A listing of these documents is contained in the evaluation report. The manufacturer has declared that certain submitted materials contain proprietary information and should not be subject to public disclosure.

Recommended Applications

The assay is for the semiquantitative determination of BTEX in water and soil. "BTEX" is a term of convenience for the sum of benzene, toluene, ethyl benzene, and xylenes as determined by compound-specific analyses. "BTEX" measurements also serve as an indicator for the presence of petroleum fuels which contain varying concentrations of these compounds. The D TECH BTEX system is a semiquantitative assay which responds to low-molecular aromatics and some related compounds. It is initially calibrated with a pure mixture of BTEX as described above. Through appropriate recalibration, its response can be related to concentrations of specific petroleum fuels, resulting in a predictable relationship between immunoassay and reference methods for these products. In the case of BTEX assays (as with Total Petroleum Hydrocarbon, TPH assays), the correlation between immunoassay results and laboratory reference testing results can change for three reasons:

(a) Petroleum fuels are reformulated from time to time by geographic region, by season, or on a national scale to meet air pollution or other requirements. Reformulation may include the addition of non-hydrocarbon chemicals which may or nay not react in the assay.

(b) Laboratory reference methods for total petroleum hydrocarbons may be revised, resulting in an altered response relative to an immunoassay and a need to update the assay's calibration or interpretation.

(c) In water and soil, the composition of petroleum products changes as a result of solution, volatilization, chemical oxidation, and biodegradation. especially benzene, like the lower alkanes, may be lost through volatilization. In the presence of water, benzene is lost by solubilization; lower aromatics, like the linear alkanes, are potentially lost by biodegradation.

Therefore, in both site characterizations and remediations, BTEX-specific immunoassays may need recalibration by parallel testing with an applicable regulatory laboratory method and determination of an appropriate conversion factor. Without such adjustment, results can be either high or low, depending on the affinity of the assay's antibodies for the target mixture.

Semiquantitative determinations will provide responses, interpreted as either positive or negative, at one or several predetermined detection or target levels. Target levels are usually chosen to have relevance to a specific situation.

In each application of the assay, the probability of false negative and false positive results disclosed by the manufacturer should be considered. To lower the false negative rate (at the expense of raising the false positive rate), the user can adopt a higher detection level without otherwise changing the test. This may be desirable in site investigations, where the false negative rate is critical and kept as low as is appropriate for the decision(s) to be made. In site remediations, however, lowering the false positive rate is important, and a lower target level may be adopted for the same assay.

Independent validation of immunoassay results is also important in the use of both BTEX and the Total Petroleum Hydrocarbon (TPH) testing kits, because the human toxicity of the chemical species of the mixtures referred to as "BTEX" or "TPH" does not necessarily parallel their reactivity in an immunoassay. This particularly applies to benzene which, in contrast to its human toxicity, reacts only weakly in the immunoassay. Therefore, the immunoassay testing is no substitute for those complex scientific methods which more specifically allow to determine potential health and environmental risks associated with petroleum hydrocarbons.

A comprehensive process of developing data quality objectives (DQO) was published by U.S. EPA under the U.S. Superfund program. It provides guidance for analytical method QA/QC as applied to field investigations of contaminated soils. The process is intended for site-specific sampling plans. Here the immunoassay would generally qualify as a level 2 (field analysis) method, subject to confirmation by a level 3 method (confirmation and quantitation) applied predominantly to positive results. We recommend that minimum quality control should include a method blank and duplicates at five percent, or one per batch or per matrix, whichever is more frequent, in addition to the samples required for confirmation. The use of proficiency evaluation and spiked samples depends on project-specific needs.

U.S. EPA Method 602, and SW-846 Methods 8020/8021 (packed and capillary column gas chromatography), and 8240/8260 (packed and capillary column gas chromatography/mass spectrometry) are approved for the confirmation of BTEX identification and quantitation. The LUFT TPH Method, a modification of U.S. EPA Method 8015 (gas chromatography with flame-ionization detector), is approved for Leaking Underground Fuel Tank (LUFT) investigations in California.

Screening and Preliminary Site Investigations

The immunoassay can assist in site investigations, if there are compelling historical data to indicate the presence of BTEX (e.g., oil spill, handling or processing of petroleum fuels). If used on samples of largely unknown composition, without prior characterization by a fully qualitative and quantitative laboratory method, confirmatory analysis is needed for every positive immunoassay result. No negative determinations can be made without taking into account the specificity of the assay and its possible susceptibility to interferences and matrix effects. Benzene may pose a special problem, because it reacts only weakly in the various immunoassays, but is also one of the most volatile components, and the most water soluble and most toxic of many petroleum products.

In the absence of other regulations and guidelines, we recommend that assay results be confirmed in the following manner:

(a) For the delineation of BTEX or petroleum fuel contamination in a coherent mass of soil, the required frequency of confirmation by an approved method resulting in identification and quantification should be one for every ten, or a fraction thereof, samples testing positive at the target or action level applicable at the site.

(b) One of every ten, or fraction thereof, negative results should be confirmed.

Site Investigations and Remedial Actions

For remedial investigations or RCRA facility investigations, testing usually proceeds under a site-specific Quality Assurance Project Plan (QAPP). Immunoassay and other field measurements are "bracketed" in time and space by qualitative and fully quantitative analyses. Generally, a site is first characterized by the use of approves, fully qualitative and quantitative analytical methods as to the nature and level of contamination in key sampling locations and as to the presence of substances that may interfere with the use of the immunoassay. The immunoassay can then be used in the comprehensive mapping of the site with respect to identified contaminant(s) to which the immunoassay responds. A specified percentage of samples that would be confirmed by another approved, fully quantitative method would be as stipulated in the QAPP; the project manager could call for additional confirmatory testing if indicated in the course of the investigation. During site cleanup, the QAPP would provide for use of the immunoassay to monitor progress. Confirmatory laboratory testing would occur before a decision on site closure is made.

Regulatory Implications

This immunoassay has been accepted as a Draft Method by the U.S. EPA Office of Solid Waste as Method 4031 (SW-846 Manual of Methods). DTSC's certification does not change the regulatory status of BTEX testing; it should, however, facilitate and encourage the acceptance of this technology where a project's data quality objectives can be met by its use. To this end, DTSC's findings should contribute to a consideration of this technology in regulated activities, depending on each regulated program's objectives and constraints.

State-regulated disposal facilities may contact state permitting officers for use of the immunoassay for operational monitoring. Other local and state government permitting authorities may taken this certification under consideration when making their permitting decisions. Other project leaders may consider using this assay if a project's data quality objectives can be met by its use.